Molecular Systematics And Phylogenetics Of Gracilariacean Species Based On Cox1,5.8S RDNA-ITS, RbcL And Rbc Spacer

Gracilariacean species are widely distributed and has great variety in the world,also with high economic value. But because of their wide variety, phenotypicplasticity and other reasons, there are mang remaining taxonomic problems of genusidentification and species identification. To analyze nucleotide diversity andphylogeny of Gracilariaceae (Gracilariales, Rhodophyta), we compared mitochondrialcox1(partial), chloroplast rbcL and rbc spacer (complete), nuclear5.8S rDNA-ITS(complete) sequences of twenty four populations of five Gracilaria andGracilariopsis species (Gracilariaceae, Rhodophyta), with cox1, rbcL,5.8SrDNA-ITS, rbc spacer sequences of Gracilariaceaen species downloaded fromGenBank database. The length of cox1and rbcL sequences were713bp and1467bprespectively, only660bp of cox1and1390bp of rbcL used for subsequent analysis.the length of5.8S rDNA-ITS and rbc spacer sequences was different in variousspecies, varies from893to1508bp and65to131bp respectively. The intraspecificgenetic distance of cox1, rbcL,5.8S rDNA-ITS, rbc spacer in five species which usedin this study ranges from0.002to0.006,0.001to0.002,0.000to0.004,0.000to0.006respectively, and the number of variable sites ranges from3to11,2to17,2to10,1to3respectively, all fives species had low genetic variation between and withinpopulations. We found there were1mutant site of cox1,1mutant site of rbcL,9mutant sites of5.8S rDNA-ITS can be used to distinguish three populations of G.vermiculophylla from China, Russia and USA; At the same time the haplotypeanalysis shows, the three geographical groups each have unique haplotypes. In thisstudy we also found there are a few of closely relate species in Gracilariaceae, such asGracilariopsis lemaneiformis and Gracilaria chorda, the genetic distance of rbcLbetween two spacies was0.001which far lower than species level. Due to the absence of cox1,5.8S rDNA-ITS and rbc spacer in Gracilaria chorda, we could not be so suretheir phylogenetic relationship which need a further study. Except for closely relatespecies, the interspecific genetic distance between species of cox1, rbcL,5.8SrDNA-ITS, rbc spacer are rangs from0.072to0.193,0.021to0.197,0.041to0.578,0.019to0.767respectively, much higer than intraspecific genetic distance.5.8Ssequences of Gracilariaceae has low variation among species and among populations,but the distinct sites were found among the genuses and can be used on genus level orabove. Three Phylogenetic tree were constructed based on cox1, rbcL and5.8SrDNA-ITS respectively and showed that three main lineages of Gracilariaceae were formed:Gracilaria/Hydropuntia clade, Gracilariopsis/Gracilariophila clade and Melanthalia clade,Melanthalia clade is the earliest differentiation branch based on the fact that which isat the bottom of the phylogenetic tree; In the phylogenetic tree, Hydropuntia specieswere not formed into one clade and Gracilariopsis species were formed into one clade,we suggested that Hydropuntia should be regarded as a taxonomic category belowGracilaria genus of Gracilaria, at the same time our results supported the point of view thatGracilariopsis should be a separate genus.